Progress Monitoring

Handle progress notifications from long-running server operations.

New in version 2.3.5

MCP servers can report progress during long-running operations. The client can receive these updates through a progress handler.

Progress Handler

Set a progress handler when creating the client:

from fastmcp import Client

async def my_progress_handler(
    progress: float, 
    total: float | None, 
    message: str | None
) -> None:
    if total is not None:
        percentage = (progress / total) * 100
        print(f"Progress: {percentage:.1f}% - {message or ''}")
    else:
        print(f"Progress: {progress} - {message or ''}")

client = Client(
    "my_mcp_server.py",
    progress_handler=my_progress_handler
)

Handler Parameters

The progress handler receives three parameters:

Progress Handler Parameters

progress · float

Current progress value

total · float | None

Expected total value (may be None)

message · str | None

Optional status message (may be None)

Per-Call Progress Handler

Override the progress handler for specific tool calls:

async with client:
    # Override with specific progress handler for this call
    result = await client.call_tool(
        "long_running_task", 
        {"param": "value"}, 
        progress_handler=my_progress_handler
    )